The cars, trucks and other vehicles driven by gasoline fuel internal combustion engines today are designed with an on-board computer to electronically control the various systems and devices contained in these vehicles.
As is well-known in the art, the basic components of a typical prior art electronically-controlled fuel metering system in such vehicles are generally as follows:
1. a fuel tank; PA1 2. an electric fuel pump, often mounted in the fuel tank; PA1 3. a pressure regulator for maintaining the pressure of the fuel supplied by the pump at a required constant pressure; PA1 4. sensors appropriately mounted on the engine or vehicle, each producing an electrical signal representative of the various conditions under which the engine must operate, in accordance with which the quantity of fuel supplied to the engine is to be controlled; PA1 5. a solenoid-operated or other suitable electrically-controlled fuel injector(s) for supplying a metered quantity of pressure-regulated fuel to the engine fuel induction system or to the individual engine cylinders; PA1 6. an electronic control unit for receiving, as inputs thereto, the electric signals generated by the sensors and producing, as the output therefrom, a single integrated electrical signal for controlling the injector(s); PA1 7. a direct current electrical power source, such as a battery and/or an alternator; PA1 8. appropriate electrical switches and conductors (electrical circuit) connecting the electrical/electronic components (electrical circuit) of the system; and PA1 9. appropriate fuel conduits connecting the fuel components (hydraulic circuit) of the system. PA1 a. Substantial energy (gasoline to provide the required power) is being wasted pumping fuel, to approximately 30-40 psi, and consuming very little (about 20%) of the total pumped fuel. PA1 b. Vapor is being churned out of the fuel, which also requires energy and reduces fuel economy. PA1 c. Pumping any fluid to high pressure creates heat that must be dissipated somehow. This is specially true in gasoline engines where the injectors are designed to and must meter liquid fuel, rather than fuel vapors. It is understood that various automotive vehicle manufacturers and others are going to the expense of trying to develop ways to dissipate this heat to cure well known vapor and other hot fuel handling problems.
The fuel pump component of current state of the art systems is typically a positive displacement electric pump activated by turning the vehicle ignition switch to the ON position and designed to constantly supply the maximum quantity of fuel that will be required by the engine under the most severe conditions of speed, load, low ambient temperatures, etc., with all other power-demanding systems (air conditioning, heater, radio, lights, windshield wipers, etc.) operating.
However, since much more than 50% (possibly as much as 90%) of normal vehicle operation requires only a very small portion (possibly about 20%) of the above-mentioned constant, total, maximum-required fuel pump output, it is necessary to by-pass the excess fuel (pumped to 30-40 psi) not required by the engine during most normal operating conditions back to the fuel tank or to sump pressure, through a by-pass conduit that normally carries a much greater volume of fuel than the conduit carrying fuel to be consumed in the engine cylinders. Obviously, total pumped fuel equals consumed fuel plus by-passed fuel.
Such fuel by-pass systems, especially where the by-passed fuel greatly exceeds the consumed fuel, creates and experiences serious inherent problems, such as the following, for example: